When two heterosexual males shove their fists into each other’s asshole. This could be done either for pleasure, or to show each other that they will do anything for them.
A thumbs-up brofist is the act of brofisting your brosef, possibly while drinking brooskis, while making a thumbs-up with your hand, and turning it sideways in a fluent motion.
"I was talking with my brosef over some beers, and when he chugged that brooski, a brofist wasn't enough. I made a thumbs-up, gave the signal, turned it sideways, and thumbs-up brofisted him.
BRO FIST is the closest bond shared by bro's in a moment of eccentricawesomeness! Often expressed by two close friends (bro's) knuckle touching eachother or bro fisting.
Guy 1:Hey what were you doing with Mike last night? I heard you two up for hours.
Guy 2:Oh we were just brofisting. Its a bro thing, dude. No homo, no worries.